This result is highly significant and implies that a country that is located 1000 km closer to the equator could expect 33% fewer cases per million inhabitants, other things equal (given that a degree of latitude translates on average into a distance of 111 km). In the ordinary least squares (OLS) regression, in which we control for all potential confounding factors, an increase in the distance from the equator by one degree of latitude is associated with an increase of the prevalence of COVID-19 by about 4.3% (Table 1, Model 4). 1 and in the coefficient estimates of latitude (which represent semi-elasticities, i.e., percentage changes in the number of COVID-19 cases per million for one-degree changes in latitude), in the different regression specifications shown in Table 1. This relationship is visible in the scatterplot in Fig. In general, the farther a country is located from the equator, the more cases the country has relative to the number of inhabitants. To control for key confounders at the country-level, our analysis includes (1) data on air travel 16 (to capture a possible way of transmission of SARS-CoV-2 across countries but also the remoteness of a place, which might increase the need for air travel) (2) vehicle concentration 17 and urbanization 16 (to capture differences in the transmission potential of SARS-CoV-2 within a country 18) (3) COVID-19 testing intensity 19, 20 (to control for the vigor of a country’s COVID-19 response and for COVID-19 detection bias in cross-country comparisons 21, 22) (4) cell phone usage 16 (to control for the speed at which information on behavior change for COVID-19 prevention travels within a country 18, 23) and (5) health expenditure (to capture differences in countries' commitment to population health) old-age dependency ratio (to capture cross-country differences in age structure and family compositions, which can affect the spread of SARS-CoV-2), and income 16 (to control for differences in economic development and in the availability of general resources to contain the spread of SARS-CoV-2 24, 25, 26).įigure 1 and Table 1 show our results. National Academies of Sciences, Engineering, and Medicine concluded that “although experimental studies show a relationship between higher temperatures and humidity levels, and reduced survival of SARS-CoV-2 in the laboratory, there are many other factors besides environmental temperature, humidity, and survival of the virus outside of the host that influence and determine transmission rates among humans in the ‘real world’… with natural history studies, the conditions are relevant and reflect the real-world, but there is typically little control of environmental conditions and there are many confounding factors” 4. On March 9, 2020, the World Health Organization (WHO) stated that “from the evidence so far, the COVID-19 virus can be transmitted in all areas, including areas with hot and humid weather” 5.
However, in the context of coronavirus disease 2019 (COVID-19), the disease caused by SARS-CoV-2, there is still scant evidence in support of this hypothesis 4. Rather, the higher temperatures and more intense UV radiation in summer are likely to support public health measures to contain SARS-CoV-2. However, our results do not imply that the disease will vanish during summer or will not affect countries close to the equator.
According to our results, countries are expected to see a decline in new COVID-19 cases during summer and a resurgence during winter. Since the change in Earth’s angle towards the sun between equinox and solstice is about 23.5°, one could expect a difference in cases per million inhabitants of 64% between two hypothetical countries whose climates differ to a similar extent as two adjacent seasons. Our results imply that a country, which is located 1000 km closer to the equator, could expect 33% fewer cases per million inhabitants.
A one-degree increase in absolute latitude is associated with a 4.3% increase in cases per million inhabitants as of Janu(p value < 0.001). We regress the logarithm of confirmed COVID-19 cases per million inhabitants in a country against the country’s distance from the equator, controlling for key confounding factors: air travel, vehicle concentration, urbanization, COVID-19 testing intensity, cell phone usage, income, old-age dependency ratio, and health expenditure.
Sun corona vs center temperature how to#
Scientists disagree how to interpret this observation because the relationship between COVID-19 and climatic conditions may be confounded by many factors. Visual inspection of world maps shows that coronavirus disease 2019 (COVID-19) is less prevalent in countries closer to the equator, where heat and humidity tend to be higher.